Trojans are malicious computers programs that infect devices/systems by mimicking genuine software and then going on to extract data from the system/device. Using third-party apps, some of which may even be Trojan apps, might cause all your banking-related data to end up in the hands of cyber criminals, who may either misuse the data themselves or sell them off to others. The best policy would be to always download or purchase apps from the authorized app stores, like Google Play Store or the Apple Play Store.”]
Source: https://hackercombat.com/how-to-identify-and-combat-trojans-on-unauthorized-financial-apps/